#define _CRT_SECURE_NO_WARNINGS 1

#include <iostream>
using namespace std;
int main() {
	int w, h;
	cin >> w >> h;
	int h1 = h + 2;
	int w1 = w + 2;
	int count = 0;
	int arr[h1 + 2][w1 + 2];
	for (int i = 2; i < h1; i++) {
		for (int j = 2; j < w1; j++) {
			if (arr[i + 2][j] != 1 && arr[i - 2][j] != 1 && arr[i][j + 2] != 1 && arr[i][j - 2] != 1)
			{
				arr[i][j] = 1;
				count++;
			}
		}
	}
	cout << count;
}
